A combustion section of a gas turbine generally includes a plurality of combustors that are arranged in an annular array around an outer casing such as a compressor discharge casing. Compressed air flows from a compressor to the compressor discharge casing and is routed to each combustor. Fuel from a fuel nozzle is mixed with the compressed air in each combustor to form a combustible mixture within a primary combustion zone of the combustor. The combustible mixture is burned to produce hot combustion gases having a high pressure and high velocity. The combustion gases are routed along a hot gas path defined within the compressor discharge casing towards a first stage of stationary turbine nozzles that are mounted upstream from and/or adjacent to an inlet of a turbine. The combustion gases flow across the turbine nozzles which direct the combustion gases across a stage of turbine blades which are connected to a shaft. Thermal and kinetic energy are transferred from the combustion gases to the turbine blades to cause the shaft to rotate, thereby producing mechanical work. For example, the turbine may be coupled to a shaft that drives a generator to produce electricity.
In particular gas turbine designs, a system for supporting the first stage of turbine nozzles includes an inner barrel or diffuser casing that extends downstream from the compressor within the compressor discharge casing. The diffuser casing defines a flow path for routing the compressed air between the compressor and the compressor discharge casing. A nozzle support ring is bolted to an aft portion of the diffuser casing and extends axially and/or radially between the diffuser casing and the first stage of turbine nozzles to provide mounting support for the turbine nozzles.
As power output requirements of gas turbines continue to increase, the size or overall footprint of the gas turbines also increases. This requires larger facilities to accommodate the larger gas turbines and may increase costs associated with and/or prohibit replacing existing gas turbines with newer designs. As a result, designers are tasked with balancing size, particularly the axial length, of newer gas turbines with the increased power output requirements. One area of the gas turbine that may be shortened while maintaining desired power output and overall efficiency of the gas turbine is the combustion section. However, a shorter diffuser may compromise compressor efficiency. As a result, it is preferable to shorten the axial length between the aft portion of the diffuser and the first stage turbine nozzles, thereby rendering existing support schemes less than optimal. As a result, an improved system for supporting the first stage of turbine nozzles which accommodates for the shorter combustion section would be useful.